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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
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15 include "formal_topology/relations.ma".
16 include "datatypes/categories.ma".
18 definition is_saturation ≝
19 λC:REL.λA:unary_morphism (Ω \sup C) (Ω \sup C).
20 ∀U,V. (U ⊆ A V) = (A U ⊆ A V).
22 definition is_reduction ≝
23 λC:REL.λJ:unary_morphism (Ω \sup C) (Ω \sup C).
24 ∀U,V. (J U ⊆ V) = (J U ⊆ J V).
26 theorem subseteq_refl: ∀A.∀S:Ω \sup A.S ⊆ S.
30 theorem subseteq_trans: ∀A.∀S1,S2,S3: Ω \sup A. S1 ⊆ S2 → S2 ⊆ S3 → S1 ⊆ S3.
31 intros; apply transitive_subseteq_operator; [apply S2] assumption.
34 theorem saturation_expansive: ∀C,A. is_saturation C A → ∀U. U ⊆ A U.
35 intros; apply (fi ?? (H ??)); apply subseteq_refl.
38 theorem saturation_monotone:
39 ∀C,A. is_saturation C A →
40 ∀U,V. U ⊆ V → A U ⊆ A V.
41 intros; apply (if ?? (H ??)); apply subseteq_trans; [apply V|3: apply saturation_expansive ]
45 theorem saturation_idempotent: ∀C,A. is_saturation C A → ∀U. A (A U) = A U.
47 [ apply (if ?? (H ??)); apply subseteq_refl
48 | apply saturation_expansive; assumption]
51 record basic_topology: Type ≝
53 A: unary_morphism (Ω \sup carrbt) (Ω \sup carrbt);
54 J: unary_morphism (Ω \sup carrbt) (Ω \sup carrbt);
55 A_is_saturation: is_saturation ? A;
56 J_is_reduction: is_reduction ? J;
57 compatibility: ∀U,V. (A U ≬ J V) = (U ≬ J V)
60 (* the same as ⋄ for a basic pair *)
61 definition image: ∀U,V:REL. binary_morphism1 (arrows1 ? U V) (Ω \sup U) (Ω \sup V).
62 intros; constructor 1;
63 [ apply (λr: arrows1 ? U V.λS: Ω \sup U. {y | ∃x:U. x ♮r y ∧ x ∈ S});
64 intros; simplify; split; intro; cases H1; exists [1,3: apply w]
65 [ apply (. (#‡H)‡#); assumption
66 | apply (. (#‡H \sup -1)‡#); assumption]
67 | intros; split; simplify; intros; cases H2; exists [1,3: apply w]
68 [ apply (. #‡(#‡H1)); cases x; split; try assumption;
69 apply (if ?? (H ??)); assumption
70 | apply (. #‡(#‡H1 \sup -1)); cases x; split; try assumption;
71 apply (if ?? (H \sup -1 ??)); assumption]]
74 (* the same as □ for a basic pair *)
75 definition minus_star_image: ∀U,V:REL. binary_morphism1 (arrows1 ? U V) (Ω \sup U) (Ω \sup V).
76 intros; constructor 1;
77 [ apply (λr: arrows1 ? U V.λS: Ω \sup U. {y | ∀x:U. x ♮r y → x ∈ S});
78 intros; simplify; split; intros; apply H1;
79 [ apply (. #‡H \sup -1); assumption
80 | apply (. #‡H); assumption]
81 | intros; split; simplify; intros; [ apply (. #‡H1); | apply (. #‡H1 \sup -1)]
82 apply H2; [ apply (if ?? (H \sup -1 ??)); | apply (if ?? (H ??)) ] assumption]
85 (* minus_image is the same as ext *)
87 theorem image_id: ∀o,U. image o o (id1 REL o) U = U.
88 intros; unfold image; simplify; split; simplify; intros;
89 [ change with (a ∈ U);
90 cases H; cases x; change in f with (eq1 ? w a); apply (. f‡#); assumption
91 | change in f with (a ∈ U);
92 exists; [apply a] split; [ change with (a = a); apply refl | assumption]]
95 theorem minus_star_image_id: ∀o,U. minus_star_image o o (id1 REL o) U = U.
96 intros; unfold minus_star_image; simplify; split; simplify; intros;
97 [ change with (a ∈ U); apply H; change with (a=a); apply refl
98 | change in f1 with (eq1 ? x a); apply (. f1 \sup -1‡#); apply f]
101 theorem image_comp: ∀A,B,C,r,s,X. image A C (r ∘ s) X = image B C r (image A B s X).
102 intros; unfold image; simplify; split; simplify; intros; cases H; clear H; cases x;
103 clear x; [ cases f; clear f; | cases f1; clear f1 ]
104 exists; try assumption; cases x; clear x; split; try assumption;
105 exists; try assumption; split; assumption.
108 theorem minus_star_image_comp:
110 minus_star_image A C (r ∘ s) X = minus_star_image B C r (minus_star_image A B s X).
111 intros; unfold minus_star_image; simplify; split; simplify; intros; whd; intros;
112 [ apply H; exists; try assumption; split; assumption
113 | change with (x ∈ X); cases f; cases x1; apply H; assumption]
116 record continuous_relation (S,T: basic_topology) : Type ≝
117 { cont_rel:> arrows1 ? S T;
118 reduced: ∀U. U = J ? U → image ?? cont_rel U = J ? (image ?? cont_rel U);
119 saturated: ∀U. U = A ? U → minus_star_image ?? cont_rel U = A ? (minus_star_image ?? cont_rel U)
122 definition continuous_relation_setoid: basic_topology → basic_topology → setoid1.
123 intros (S T); constructor 1;
124 [ apply (continuous_relation S T)
126 [ apply (λr,s:continuous_relation S T.∀b. A ? (ext ?? r b) = A ? (ext ?? s b));
127 | simplify; intros; apply refl1;
128 | simplify; intros; apply sym1; apply H
129 | simplify; intros; apply trans1; [2: apply H |3: apply H1; |1: skip]]]
132 definition cont_rel': ∀S,T: basic_topology. continuous_relation_setoid S T → arrows1 ? S T ≝ cont_rel.
136 definition cont_rel'': ∀S,T: basic_topology. continuous_relation_setoid S T → binary_relation S T ≝ cont_rel.
144 ∀x. ext ?? (b∘a) x = extS ?? a (ext ?? b x).
146 unfold ext; unfold extS; simplify; split; intro; simplify; intros;
147 cases f; clear f; split; try assumption;
148 [ cases f2; clear f2; cases x1; clear x1; exists; [apply w] split;
149 [1: split] assumption;
150 | cases H; clear H; cases x1; clear x1; exists [apply w]; split;
151 [2: cases f] assumption]
155 (* this proof is more logic-oriented than set/lattice oriented *)
156 theorem continuous_relation_eqS:
157 ∀o1,o2:basic_topology.∀a,a': continuous_relation_setoid o1 o2.
158 a = a' → ∀X. A ? (extS ?? a X) = A ? (extS ?? a' X).
160 cut (∀a: arrows1 ? o1 ?.∀x. x ∈ extS ?? a X → ∃y:o2.y ∈ X ∧ x ∈ ext ?? a y);
161 [2: intros; cases f; clear f; cases H1; exists [apply w] cases x1; split;
162 try assumption; split; assumption]
163 cut (∀a,a':continuous_relation_setoid o1 o2.eq1 ? a a' → ∀x. x ∈ extS ?? a X → ∃y:o2. y ∈ X ∧ x ∈ A ? (ext ?? a' y));
164 [2: intros; cases (Hcut ?? f); exists; [apply w] cases x1; split; try assumption;
166 apply (saturation_expansive ?? (A_is_saturation o1) (ext ?? a1 w) x);
167 assumption;] clear Hcut;
168 split; apply (if ?? (A_is_saturation ???)); intros 2;
169 [lapply (Hcut1 a a' H a1 f) | lapply (Hcut1 a' a (H \sup -1) a1 f)]
170 cases Hletin; clear Hletin; cases x; clear x;
171 cut (∀a: arrows1 ? o1 ?. ext ?? a w ⊆ extS ?? a X);
172 [2,4: intros 3; cases f3; clear f3; simplify in f5; split; try assumption;
173 exists [1,3: apply w] split; assumption;]
174 cut (∀a. A ? (ext o1 o2 a w) ⊆ A ? (extS o1 o2 a X));
175 [2,4: intros; apply saturation_monotone; try (apply A_is_saturation); apply Hcut;]
176 apply Hcut2; assumption.
180 theorem continuous_relation_eq':
181 ∀o1,o2.∀a,a': continuous_relation_setoid o1 o2.
182 a = a' → ∀X.minus_star_image ?? a (A o1 X) = minus_star_image ?? a' (A o1 X).
183 intros; split; intro; unfold minus_star_image; simplify; intros;
184 [ cut (ext ?? a a1 ⊆ A ? X); [2: intros 2; apply (H1 a2); cases f1; assumption;]
185 lapply (if ?? (A_is_saturation ???) Hcut); clear Hcut;
186 cut (A ? (ext ?? a' a1) ⊆ A ? X); [2: apply (. (H ?)‡#); assumption]
187 lapply (fi ?? (A_is_saturation ???) Hcut);
188 apply (Hletin1 x); change with (x ∈ ext ?? a' a1); split; simplify;
189 [ apply I | assumption ]
190 | cut (ext ?? a' a1 ⊆ A ? X); [2: intros 2; apply (H1 a2); cases f1; assumption;]
191 lapply (if ?? (A_is_saturation ???) Hcut); clear Hcut;
192 cut (A ? (ext ?? a a1) ⊆ A ? X); [2: apply (. (H ?)\sup -1‡#); assumption]
193 lapply (fi ?? (A_is_saturation ???) Hcut);
194 apply (Hletin1 x); change with (x ∈ ext ?? a a1); split; simplify;
195 [ apply I | assumption ]]
198 theorem extS_singleton:
199 ∀o1,o2.∀a:arrows1 ? o1 o2.∀x.extS o1 o2 a (singleton o2 x) = ext o1 o2 a x.
200 intros; unfold extS; unfold ext; unfold singleton; simplify;
201 split; intros 2; simplify; cases f; split; try assumption;
202 [ cases H; cases x1; change in f2 with (eq1 ? x w); apply (. #‡f2 \sup -1);
204 | exists; try assumption; split; try assumption; change with (x = x); apply refl]
207 theorem continuous_relation_eq_inv':
208 ∀o1,o2.∀a,a': continuous_relation_setoid o1 o2.
209 (∀X.minus_star_image ?? a (A o1 X) = minus_star_image ?? a' (A o1 X)) → a=a'.
211 cut (∀a,a': continuous_relation_setoid o1 o2.
212 (∀X.minus_star_image ?? a (A o1 X) = minus_star_image ?? a' (A o1 X)) →
213 ∀V:o2. A ? (ext ?? a' V) ⊆ A ? (ext ?? a V));
214 [2: clear b H a' a; intros;
215 lapply depth=0 (λV.saturation_expansive ??? (extS ?? a V)); [2: apply A_is_saturation;|skip]
216 (* fundamental adjunction here! to be taken out *)
217 cut (∀V:Ω \sup o2.V ⊆ minus_star_image ?? a (A ? (extS ?? a V)));
218 [2: intro; intros 2; unfold minus_star_image; simplify; intros;
219 apply (Hletin V1 x); whd; split; [ exact I | exists; [apply a1] split; assumption]]
221 cut (∀V:Ω \sup o2.V ⊆ minus_star_image ?? a' (A ? (extS ?? a V)));
222 [2: intro; apply (. #‡(H ?)); apply Hcut] clear H Hcut;
223 (* second half of the fundamental adjunction here! to be taken out too *)
224 intro; lapply (Hcut1 (singleton ? V)); clear Hcut1;
225 unfold minus_star_image in Hletin; unfold singleton in Hletin; simplify in Hletin;
226 whd in Hletin; whd in Hletin:(?→?→%); simplify in Hletin;
227 apply (if ?? (A_is_saturation ???));
228 intros 2 (x H); lapply (Hletin V ? x ?);
229 [ apply refl | cases H; assumption; ]
230 change with (x ∈ A ? (ext ?? a V));
231 apply (. #‡(†(extS_singleton ????)));
233 split; apply Hcut; [2: assumption | intro; apply sym1; apply H]
236 definition continuous_relation_comp:
238 continuous_relation_setoid o1 o2 →
239 continuous_relation_setoid o2 o3 →
240 continuous_relation_setoid o1 o3.
241 intros (o1 o2 o3 r s); constructor 1;
245 apply (.= †(image_comp ??????));
246 apply (.= (reduced ?????)\sup -1);
247 [ apply (.= (reduced ?????)); [ assumption | apply refl1 ]
248 | apply (.= (image_comp ??????)\sup -1);
252 apply (.= †(minus_star_image_comp ??????));
253 apply (.= (saturated ?????)\sup -1);
254 [ apply (.= (saturated ?????)); [ assumption | apply refl1 ]
255 | apply (.= (minus_star_image_comp ??????)\sup -1);
259 definition BTop: category1.
261 [ apply basic_topology
262 | apply continuous_relation_setoid
263 | intro; constructor 1;
266 apply (.= (image_id ??));
268 apply (.= †(image_id ??));
272 apply (.= (minus_star_image_id ??));
274 apply (.= †(minus_star_image_id ??));
277 | intros; constructor 1;
278 [ apply continuous_relation_comp;
279 | intros; simplify; intro x; simplify;
280 lapply depth=0 (continuous_relation_eq' ???? H) as H';
281 lapply depth=0 (continuous_relation_eq' ???? H1) as H1';
282 letin K ≝ (λX.H1' (minus_star_image ?? a (A ? X))); clearbody K;
284 minus_star_image o2 o3 b (A o2 (minus_star_image o1 o2 a (A o1 X)))
285 = minus_star_image o2 o3 b' (A o2 (minus_star_image o1 o2 a' (A o1 X))));
286 [2: intro; apply sym1; apply (.= #‡(†((H' ?)\sup -1))); apply sym1; apply (K X);]
289 minus_star_image o1 o3 (b ∘ a) (A o1 X) = minus_star_image o1 o3 (b'∘a') (A o1 X));
291 apply (.= (minus_star_image_comp ??????));
292 apply (.= #‡(saturated ?????));
293 [ apply ((saturation_idempotent ????) \sup -1); apply A_is_saturation ]
295 apply (.= (minus_star_image_comp ??????));
296 apply (.= #‡(saturated ?????));
297 [ apply ((saturation_idempotent ????) \sup -1); apply A_is_saturation ]
298 apply ((Hcut X) \sup -1)]
299 clear Hcut; generalize in match x; clear x;
300 apply (continuous_relation_eq_inv');
302 | intros; simplify; intro; do 2 (unfold continuous_relation_comp); simplify;
303 apply (.= †(ASSOC1‡#));
305 | intros; simplify; intro; unfold continuous_relation_comp; simplify;
306 apply (.= †((id_neutral_right1 ????)‡#));
308 | intros; simplify; intro; simplify;
309 apply (.= †((id_neutral_left1 ????)‡#));